Larval morphology of Arrenurus cuspidifer Piersig, A. claviger Koenike, and A. latus Barrois & Moniez (Acari: Hydrachnidia) Author Zawal, Andrzej text Zootaxa 2006 1276 55 68 journal article 10.5281/zenodo.173333 e4bc0cd0-a1b8-4be5-9e50-d5b676cf9d3f 1175­5326 173333 Arrenurus cuspidifer Piersig, 1986 (76, 90) ( Fig. 1 , Tables 1 , 2 ) Material examined: Progeny from a single female collected from a lowland bog, near Lublin, Poland , 51o24’N , 23o24’E , among sedges, 28 May 2004 . Diagnosis: Dorsal plate egg­shaped with small anterior­lateral indentations; median margin of CpIII slightly shorter than CpII, CpI twice longer; Expp pentagonal­shaped, its width clearly exceeds its length, Exp located posterior to the centre of the plate and at the same level as the E2 setae; IITi10 long and located near IITi9, IIITi10 short, thick and located near IIITi9, IIITa13 smooth. Description: The egg­shaped dorsal plate is widest in the first third of its length and narrows in the posterior part. Its anterior margin is slightly convex and the posterior margin is rounded. Anterior­lateral indentations are small, with slightly obtuse angles, and reach to about one­quarter of the plate width and one­sixth of its length. Seta Lpl is tripartite, the remaining setae are smooth. The median margins of CpIII are slightly shorter than median margins of CpII, and CpI median margins are twice as long. The ratios of CpI/CpII/CpIII are 2.5/1.2/1. All setae on the coxal plate are smooth. Distance between the C4 seta and CpIII median margin is twice the distance between C1 and CpI median margin. Distance between setae C1 and C2 is fairly small. FIGURE 1. Morphology of the larva of Arrenurus cuspidifer : A, ventral side; B, dorsal plate; C, excretory pore plate; D, pedipalp; E, chelicera; F, leg I; G, leg II; H, leg III (explanation in text). TABLE 1. Dimensions (ųm) of individual body parts.

A. claviger (n=10) range mean standard deviation	A. cuspidifer (n=10) range mean standard deviation
length width	234–260 247.8 7.21 186–208 196.2 6.00	176–180 178.4 2.07 150–154 151.8 1.75
dorsal plate length	220–244 232.4 6.52	176–180 178.6 1.65
dorsal plate width CpI medial margin length	174–184 179.6 3.24 70–74 72.2 1.18	136–140 137.4 1.65 54–62 59.0 2.02
CpII medial margin length	42–46 43.2 1.55	28–29 28.5 0.41
CpIII medial margin length distance Mp1­Mp1	38–41 39.0 1.20 77–78 77.7 0.70	23–24 23.7 0.41 52–56 53.9 1.20
distance Lp1­Lp1	87–91 89.4 1.40	58–60 58.5 0.96
distance Lp2­Lp2 distance Mp2­Mp2	110–114 112.2 1.41 62–64 63.3 0.80	76–83 79.3 1.94 42–45 43.5 1.01
distance Mh1­Mp2	46–50 47.8 1.60	30–34 31.6 1.02
distance Mp1­Lp1 distance Mp1­Lp2	10–11 10.2 0.54 39–49 43.7 2.36	5–6 5.4 0.39 30–36 33.0 2.13
distance Mp1­Mp2	80–83 81.4 1.25	54–57 55.5 0.94
distance Mp2­Mh1 distance between C1 and CpI	28–30 28.8 0.84 20–22 21.3 0.94	18–26 22.9 1.93 13–15 14.0 0.86
distance between C4 and CpIII	31–33 32.0 0.53	27–29 27.7 0.56
distance between C1 and C2 excretory pore plate length	49–58 52.6 2.79 26–30 28.6 1.13	35–38 36.7 0.96 18–20 18.7 0.94
excretory pore plate width	27–30 28.4 0.86	22–24 22.6 0.93
distance between Exp and Expp posterior margin	16–18 17.0 0.93	6–10 7.1 1.09
distance between E1 setae and Expp anterior margin distance between E2 setae and Expp posterior margin	3–4 3.7 0.41 10–14 10.8 1.26	3–4 3.7 0.41 6–11 7.0 1.12
PI length PII length	12–14 13.1 0.56 35–38 36.2 0.93	7–8 7.7 0.41 23–25 24.2 0.51
PIII length	31–34 32.3 0.86	23–25 24.1 0.45
length of PIV claw length of cheliceral segment I	24–28 25.8 1.30 89–94 91.8 1.73	18–22 19.9 0.96 63–68 65.1 1.42
length of PV 8 seta	146–154 153.7 6.12	85–100 91.8 4.30

to be continued. TABLE 1. (continued). A. latus (n=8) A. latus ( Stechmann 1977 ) range mean standard range deviation

length 204–224	211.4	6.87	­
width 171–191	180.6	5.54	­
dorsal plate length 195–209	199.4	4.03	230–239
dorsal plate width 153–159	155.6	2.00	168–180
CpI medial margin length 66–68	67.1	0.85	68–73
CpII medial margin length 35–37	36.2	0.56	33–38
CpIII medial margin length 35–37	35.7	0.51	35–40
distance Mp1­Mp1 33–35	33.8	0.64	30–36
distance Lp1­Lp1 42–44	42.8	0.70	40–50
distance Lp2­Lp2 77–80	78.8	1.20	81–88
distance Mp2­Mp2 39–42	40.4	1.17	38–44
distance Mh1­Mp2 45–47	46.0	0.71	53–55*
distance Mp1­Lp1 8–9	8.6	0.29	­
distance Mp1­Lp2 38–40	38.9	0.56	­
distance Mp1­Mp2 56–62	59.5	2.38	60–66
distance Mp2­Mh1 18–22	20.6	1.20	36–43**
distance between C1 and CpI 18–19	18.4	0.50	20–23
distance between C4 and CpIII 29–31	29.9	0.38	­
distance between C1 and C2 42–47	44.7	2.06	55–61
excretory pore plate length 29–31	29.8	0.86	­
excretory pore plate width 29–31	29.7	0.51	­
distance between Exp and Expp 12–13 posterior margin	12.5	0.56	­
distance between E1 setae and E 7–8 xpp anterior margin	7.4	0.41	­
distance between E2 setae and E 13–14 xpp posterior margin	14.0	0.38	­
PI length 7–8	7.7	0.41	­
PII length 20–22	21.1	0.60	­
PIII length 24–26	25.4	0.75	­
length of PIV claw 18–21	19.2	1.06	­
length of cheliceral segment I 63–65	64.4	0.99	­
length of PV 8 seta 130–135	132.5	1.22	­

* Stechmann (1977) reported the Mh1­Mh1distance; the value given here was obtained by calculating [(Mh1­Mh1) ­ (Mp2­Mp2)]/2 ** Stechmann (1977) reported the Mp1­Mh1 distance; the value given here was obtained by calculating (Mp1­Mh1) ­ (Mp1­Mp2) TABLE 2. Dimensions (in ųm) of leg segments of larval Arrenurus claviger , A. cuspidifer and A. latus .

trochanter	femur	genu
range mean A. claviger (n=10) I 22–24 22.6	standard range mean standard deviation deviation 0.91 32–38 35.3 1.62	range mean standard deviation 31–35 32.5 1.20
II 28–32 30.4 III 32–34 33.0	1.31 38–40 38.7 1.01 0.74 42–46 43.1 1.58	38–40 39.4 0.74 42–45 43.6 1.02
A. cuspidifer (n=10)
I 15–16 16.0 II 20–22 20.8	0.92 22–26 24.2 1.05 0.65 25–30 27.5 1.32	24–26 25.0 1.00 26–30 27.1 1.38
III 22–23 22.4	0.53 27–29 27.9 0.70	26–28 27.3 0.7
A. latus (n=8) I 22–23 22.4	0.42 37–39 38.0 0.70	34–38 36.2 1.24
II 27–30 28.8	1.06 36–42 39.5 1.53	37–39 38.3 0.74
III 28–30 28.7	0.98 38–40 39.2 0.75	37–40 38.5 0.81
continued.
tibia	tarsus
range A. claviger (n=10) I 48–52	mean standard deviation range 50.8 1.26 67–72	mean standard deviation 68.4 1.37
II 57–60 III 56–58	58.4 1.00 80–84 57.5 0.80 84–88	82.1 1.20 85.4 1.36
A. cuspidifer (n=10)
I 36–38 II 42–44	37.6 0.84 52–54 42.5 0.96 60–62	52.9 0.70 60.5 0.56
III 43–45	44.0 0.65 59–61	59.9 0.70
A. latus (n=8) I 50–52	51.3 0.77 70–73	71.4 0.89
II 52–54	52.7 0.87 74–77	75.4 0.95
III 52–54	53.0 0.74 77–79	77.9 0.70

The excretory pore plate is pentagonal­shaped, its width clearly exceeds its length. The excretory pore is located posterior to the centre of the plate and is about at the same level as the E2 setae. The pedipalps are typical for Arrenurus species. Seta PIII1 is bipectinate, PIV1 is fairly large, all setae on PV are fairly thin and PV8 is fairly short. The first segment of the chelicerae is bottle­shaped, slightly bent posteriory and fairly short. The proportions of segments are more or less the same on each limb. The shortest segment, the trochanter, constitutes about 2/3 of the femur and genu which are of the same length; the tibia is 1.5 times longer and the tarsus 2 times longer ( Table 2 ). Tarsi of all legs (particularly those of the first leg) are fairly thick. Setae ITa13, ITa14, IITa13, IITa14 and IIITa14 are short and thin. ITi8 is short and thin, IITi10 is long and located almost in the same place as IITi9; IIITi10 is short, thick and located near IIITi9. IIITa13 is smooth.